With licensing and cost issues, can Thunderbolt break out of its niche?

Enthusiasm may have waned, but the technology should continue to spread in 2013.

Enlarge / Intel was still pimping Thunderbolt at the 2013 CES, even if vendors weren't as keen on the technology as they seemed to be last year.

Chris Foresman

Intel launched Thunderbolt in February 2011, choosing Apple as its first OEM partner. Almost two years later, the high-speed interconnect is still an expensive, niche connectivity option, despite the fact that it has spread to Windows PCs and numerous vendors have announced Thunderbolt-compatible products. As the standard begins to mature, will the technology begin to break out of its niche?

It's hard to say with absolute certainty, but it appears that the groundwork laid in 2012 may slowly start to pay off in 2013.

Cables, great and small

Unsurprisingly, as the first computer vendor to widely adopt Thunderbolt, Apple was also the first vendor out of the gate with Thunderbolt cables. However, the cables were pricey at $50 each. Some observers were practically apoplectic over the price, while others compared the price to that of other high-speed, bi-directional interconnects which often require much more exotic and expensive hardware.

Other cables eventually hit the market, but prices weren't better than what Apple offered. Semiconductor manufacturer Intersil promised that its next-generation Thunderbolt transceiver chips—a necessary component of Thunderbolt cables—would bring prices down in 2013. The improved transceivers required fewer support chips, could use lower-cost, thinner conductors, and could reduce manufacturing costs by building signal testing right into the chips themselves.

It appears that Intersil's design is beginning to pay off. At Intel's booth at CES this year, we saw new thinner, more flexible Thunderbolt cables manufactured by Japanese OEM Sumitomo. And last Friday, Apple quietly dropped the price of its 2m Thunderbolt cable from $50 to $40. It's still not down to the price of commodity USB cables, for example, but prices do appear to be going down.

Another cabling option that was promised at Thunderbolt's launch was optical cables that could run as long as 100 meters. The original version of Thunderbolt, codenamed LightPeak, was in fact originally designed as an optical interconnect. The version that Intel shipped used a copper cable that used a plug based on Apple's mini DisplayPort design, which had been adopted by VESA as an open standard. Copper cables allowed a lower-cost design while adding power transmission for bus-powered devices. But moving the transceiver into the cable also allowed the flexibility to optionally use optical cables for much longer connections when required.

Corning announced one of the first optical cable options just ahead at CES, and Intel also had some samples at its booth. Pricing has not been discussed, but optical cables tend to cost more than copper. However, if a computer needs to be located in a closet, an optical cable could be used to connect displays, storage, or other devices in the other room or even down the hall.

More devices are coming

Dozens of Thunderbolt devices, including portable and desktop hard drives, RAIDs, multiport "docks," portable video capture devices, and more were unveiled at CES, as well as NAB and Computex, in 2012. Thunderbolt was the hot new technology that was going to revolutionize high-speed data access for consumers, and the excitement of device makers was palpable.

The story was much more sedate at CES this year. Few new products were announced. LaCie showed off its large 5big five-slot RAID box in Thunderbolt form, set to ship early in the year. Seagate, Western Digital, G Technology, and others had nothing new or radical to discuss.

Enlarge/ The LaCie 5big Thunderbolt RAID was one of the few new Thunderbolt devices we saw on the 2013 CES show floor.

But some vendors were showing off products that had long been announced but have yet to ship. For instance, peripheral maker Belkin had its Thunderbolt Express Dock (first announced as far back as September 2011) in what it called a final functional form on the CES show floor last week. Belkin representatives promised the Express Dock would—for really real this time—ship in the first quarter of 2013. The launch price, which had gone up to $400 over the course of development, is now back down to $300.

Apple may also be preparing a second-generation Thunderbolt Display. Resellers have noted that inventory of the current Thunderbolt Display has begun to run dry, typically the first sign that Apple is planning a product refresh. Since the current Thunderbolt Display uses technology from previous Cinema Displays and iMacs, it seems likely a newer version would include the improved LCD panels, thinner design, and USB 3.0 support of the newest iMac models.

Still, Apple is the only vendor shipping a Thunderbolt-equipped display. We saw a Thunderbolt display from AOC at CES 2012, but we didn't see any mention of the technology from display vendors this year. Nor have we heard about AOC shipping a version of the prototype we saw last year.

What's the hold up?

More devices from more vendors would create more competition and help drive prices down. But what's holding back the flood of Thunderbolt devices, especially those from other vendors, from coming to market at a faster pace?

Part of the delay was the high cost of the first generation of Thunderbolt controller chips. Intel launched a wider range of second-generation controllers along with Ivy Bridge in 2012, and more OEMs have begun looking at ways to integrate those lower-cost chips into newer products.

But cost isn't the only consideration. Another concern has been support from OS vendors. For instance, a Belkin representative told Ars that there was a bug in OS X that prevented a USB keyboard connected to a Thunderbolt bridge from waking a Mac from sleep. That bug has since been addressed in 10.8.2, however. Intel is also continually improving Thunderbolt drivers for Windows, according to a representative we spoke to at CES.

The one final factor—one that has likely had the most impact on Thunderbolt rolling out to market—is Intel's licensing and certification process. Several vendors we have spoken to over the past year have claimed that Intel was holding up the process, cherry picking which vendors it worked with.

Though Intel had effectively denied this characterization in the past, the company explained the situation a bit differently when we spoke at CES last week. Jason Ziller, director of Thunderbolt Marketing & Planning at Intel, told Ars that Intel has "worked closely" with vendors it felt could "offer the best products" and could meet its stringent "certification requirements." The subtext seemed to be that Intel had limited resources to support and certify new products, and so it gave priority to devices that were perhaps more novel than those proposed by other makers.

Ziller suggested that licensing to a wider variety of vendors would begin to open up this year, and we could see more products being announced soon.

Bring it on

Apple isn't giving up on Thunderbolt anytime soon. All of its computers come with at least one Thunderbolt port—save the Mac Pro, which Apple CEO Tim Cook has all but promised would be upgraded in 2013. The latest Retina MacBook Pros include two Thunderbolt ports. And it appears that its Thunderbolt Display is due for a refresh sometime soon.

Though Thunderbolt hasn't exactly taken the Windows PC world by storm, several motherboard makers now offer options for built-in or add-on Thunderbolt support. And notebook makers are adding Thunderbolt as well—Intel's booth this year featured a classy-looking HP Envy Spectre Ultrabook for demonstration purposes.

Meanwhile, Thunderbolt is largely serving two main purposes right now: dock-like port expanders for thin Ultrabooks, and high-performance storage which might otherwise be connected by FireWire or even FibreChannel. With optical cabling coming soon, it will also be one of the best solutions for connecting computers to peripherals that are up to 100m away.

Even within those limited applications, however, Thunderbolt offers a price-to-performance advantage over competing technologies. And as Thunderbolt expands throughout the next year, that advantage should increase.

Promoted Comments

With the the new higher spec USB connections I really can not see TB really changing much in the market. The backwards compatibility that USB has offered has been huge... and even though TB can handle USB connections the inter-connectivity is just to expensive.

I think it has its purpose like FW, but it will not get huge consumer uptake... As there are just more consumer friendly options out - USB...

USB is crap compared to Thunderbolt. Much like older USB specs were crap compared to FireWire. What killed FireWire was higher licensing costs and companies like Sony making their own version to avoid paying to use the name and connector.

As with most new expensive high performance connections it has its uses in the professional content creation industries. If you go to NAB and other such conferences you'll see the place is full of TB devices.

TB has a distinct advantage over USB in that it's a pure hardware connection, it doesn't have the same kind of queuing latency issues that USB suffers from and so you get a much more consistent, lower latency, higher speed transfer of data. On top of that it's also bundled with the DisplayPort standard which itself is very desirable for A/V folk.

It may never become as mainstream as USB, but the simple fact it can CARRY USB may make it more likely. It isn't a single connection type, it's a transport for any and all connection types that fit within that bandwidth of 10Gbit/s, or 100Gbit/s when the shorter fibre cables start to show up. Putting the logic on the cable itself was a smart move too because you can easily retrofit higher bandwidth connections into existing ports by just getting a better cable.

I think the main reason it hasn't had as much consumer adoption thus far is down to Intel not releasing it as a PCI-E add-in card. I really wish they did this and I don't really understand why they haven't yet. Maybe they're waiting for component costs to come down or a way to solve the pass-through issue with display output in a more elegant manner than companies like ASUS currently do with their version of this (which Intel don't certify as proper Thunderbolt).

306 Reader Comments

With the the new higher spec USB connections I really can not see TB really changing much in the market. The backwards compatibility that USB has offered has been huge... and even though TB can handle USB connections the inter-connectivity is just to expensive.

I think it has its purpose like FW, but it will not get huge consumer uptake... As there are just more consumer friendly options out - USB...

There is little point to an expansion bus that mandates an active display channel. To use Thunderbolt on a PC, one must have a CPU with Intel Processor Graphics. Intel refuses to certify designs that allow for any GPU (Asus and Gigabyte both designed products that did this). Without a way to add TB to an existing system or a workstation-class system that lacks processor graphics, they effectively discourage a large part of the early adopter segment (including Apple's own Mac Pro line).

Really, who gives a shit about backwards compatibility? I want the one cable for most everything future that thunderbolt promises. So would everyone else, if they were smart. I have a damn closet full of cables as it is already. Enough is enough.

No? I was a huge fan of Thunderbolt but $50 cables are stupider than it first seemed. OMG THEYRE ACTIVE CABLEZ YOU GUYZZ!!! Who gives a rats ass? When OEM's drop 5Ghz wireless to save a dollar in cost Thunderbolt's future as a widespread interconnect is grim.

I think the relative stability of USB and incremental upgrades in specification (2.0,3.0) which boost speed significantly diminish the effectiveness of thunderbolt. I do see it solving some practical niche applications, such as 100m distances, but not anything the average consumer will want or need. When I evaluate a standard, I ask one question: Is it faster than the device I'm connecting it to? USB 3.0 is nearly as fast as SATA 3.0 and good enough to connect an external hard drive. HDMI is good enough for my monitor. Thunderbolt will only catch on if the other standards don't solve a future problem which arises. Who knows, perhaps five years from now I'll look at all my thunderbolt devices and wonder how I ever lived with the multitude of standards.

Quite the ignorant comment you made there. As much as I want the latest, greatest, fastest, most robust form of interconnect possible, backward compatibility plays a HUGE part in the vast majority of people's lives.

Just take a look at Apple's Lightning connector and all the rage that caused from their user base to get an idea of how important it is.

With the the new higher spec USB connections I really can not see TB really changing much in the market. The backwards compatibility that USB has offered has been huge... and even though TB can handle USB connections the inter-connectivity is just to expensive.

I think it has its purpose like FW, but it will not get huge consumer uptake... As there are just more consumer friendly options out - USB...

USB is crap compared to Thunderbolt. Much like older USB specs were crap compared to FireWire. What killed FireWire was higher licensing costs and companies like Sony making their own version to avoid paying to use the name and connector.

As with most new expensive high performance connections it has its uses in the professional content creation industries. If you go to NAB and other such conferences you'll see the place is full of TB devices.

TB has a distinct advantage over USB in that it's a pure hardware connection, it doesn't have the same kind of queuing latency issues that USB suffers from and so you get a much more consistent, lower latency, higher speed transfer of data. On top of that it's also bundled with the DisplayPort standard which itself is very desirable for A/V folk.

It may never become as mainstream as USB, but the simple fact it can CARRY USB may make it more likely. It isn't a single connection type, it's a transport for any and all connection types that fit within that bandwidth of 10Gbit/s, or 100Gbit/s when the shorter fibre cables start to show up. Putting the logic on the cable itself was a smart move too because you can easily retrofit higher bandwidth connections into existing ports by just getting a better cable.

I think the main reason it hasn't had as much consumer adoption thus far is down to Intel not releasing it as a PCI-E add-in card. I really wish they did this and I don't really understand why they haven't yet. Maybe they're waiting for component costs to come down or a way to solve the pass-through issue with display output in a more elegant manner than companies like ASUS currently do with their version of this (which Intel don't certify as proper Thunderbolt).

Quite the ignorant comment you made there. As much as I want the latest, greatest, fastest, most robust form of interconnect possible, backward compatibility plays a HUGE part in the vast majority of people's lives.

I too don't like to re-purchase my electronics every five years. I'm glad standards such as VGA are disappearing, but my existing VGA solutions should still have a method to work. I have an old 1280x1024 LCD monitor that works great as a second monitor, but is VGA only.*EDIT - Spelling

I don't get it, What is Thunderbolt good for, exactly, that USB 3.0 or eSATA can't do just as well? Wikipedia tells me that Thunderbolt is 10Gbps to USB 3.0's 5Gbps, but what sort of peripheral in common use has any use for that much bandwidth?

With the the new higher spec USB connections I really can not see TB really changing much in the market. The backwards compatibility that USB has offered has been huge... and even though TB can handle USB connections the inter-connectivity is just to expensive.

I think it has its purpose like FW, but it will not get huge consumer uptake... As there are just more consumer friendly options out - USB...

USB is crap compared to Thunderbolt. Much like older USB specs were crap compared to FireWire. What killed FireWire was higher licensing costs and companies like Sony making their own version to avoid paying to use the name and connector.

As with most new expensive high performance connections it has its uses in the professional content creation industries. If you go to NAB and other such conferences you'll see the place is full of TB devices.

TB has a distinct advantage over USB in that it's a pure hardware connection, it doesn't have the same kind of queuing latency issues that USB suffers from and so you get a much more consistent, lower latency, higher speed transfer of data. On top of that it's also bundled with the DisplayPort standard which itself is very desirable for A/V folk.

It may never become as mainstream as USB, but the simple fact it can CARRY USB may make it more likely. It isn't a single connection type, it's a transport for any and all connection types that fit within that bandwidth of 10Gbit/s, or 100Gbit/s when the shorter fibre cables start to show up. Putting the logic on the cable itself was a smart move too because you can easily retrofit higher bandwidth connections into existing ports by just getting a better cable.

I think the main reason it hasn't had as much consumer adoption thus far is down to Intel not releasing it as a PCI-E add-in card. I really wish they did this and I don't really understand why they haven't yet. Maybe they're waiting for component costs to come down or a way to solve the pass-through issue with display output in a more elegant manner than companies like ASUS currently do with their version of this (which Intel don't certify as proper Thunderbolt).

I would never consider USB crap... it is by far the most commonly used and most accessible connectivity option for consumers. TB has its niche, but thats it... Beyond USB you have wide band wireless connectivity. I say within 5 years we will see most all devices connected in a wireless manor.

Quite the ignorant comment you made there. As much as I want the latest, greatest, fastest, most robust form of interconnect possible, backward compatibility plays a HUGE part in the vast majority of people's lives.

Just take a look at Apple's Lightning connector and all the rage that caused from their user base to get an idea of how important it is.

You can get Thunderbolt to USB 3.0 adapters. TB is more like a road for other connection standards as much as it's a connection standard of its own. The idea of it is to make it so you can connect pretty much anything to it so you can just use a Thunderbolt controller rather than have a separate one for USB, FireWire, audio, DisplayPort, HDMI and so on. A single controller, not necessarily a single connection port can handle all of these different I/O options rather than one for each.

I think the main reason it hasn't had as much consumer adoption thus far is down to Intel not releasing it as a PCI-E add-in card. I really wish they did this and I don't really understand why they haven't yet. Maybe they're waiting for component costs to come down or a way to solve the pass-through issue with display output in a more elegant manner than companies like ASUS currently do with their version of this (which Intel don't certify as proper Thunderbolt).

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PCIE 3.0 has a maximum bandwidth comparable to Thunderbolt (~10 Gigabit with a 2.5Ghz processor ). You need a relatively new motherboard, at which point its probably easier to just integrate the port.

I think the main reason it hasn't had as much consumer adoption thus far is down to Intel not releasing it as a PCI-E add-in card. I really wish they did this and I don't really understand why they haven't yet. Maybe they're waiting for component costs to come down or a way to solve the pass-through issue with display output in a more elegant manner than companies like ASUS currently do with their version of this (which Intel don't certify as proper Thunderbolt).

PCIE 3.0 has a maximum bandwidth comparable to Thunderbolt (~10 Gigabit with a 2.5Ghz processor ). You need a relatively new motherboard, at which point its probably easier to just integrate the port.

Which is exactly what ASUS, MSI, Gygabyte, etc. are doing on their Thunderbolt enabled boards. I think that makes sense. The problem with these boards (and TB in general on a BYO system) is that unless you are going to specifically use TB, you are giving up a massive amount of PCI bandwidth for something you won't use much. You have to use a higher end board if you want a lot of PCI bandwidth and the option of using TB down the road.

Certainly not the end of the world for many applications. But it has kept me from using the TB enabled boards.

I don't see the point in Thunderbolt, other than the possibility for external GPU's (which haven't affordably materialised) and cool multiport displays. USB3 already offers crazy-fast performance, is cheap and the best part is - its completely backwards compatible. If you can't use USB3, its still a ever-useful USB2 port. You loose nothing!

If the higher-spec USB3 materialises, I think it will significantly hamper the spread of Thunderbolt. Thunderbolt is running the risk of becoming a niche product.

On the windows side I think Sony's external media dock with an external graphics card and optical drive made good use of thunderbolt, the different connector and fairly low powered graphics card were an issue but it was only a first generation device. If they could standardise that a bit and produce a better graphics card I'd love to use something like that with a Vaio duo 11 style machine (I know it doesn't have thunderbolt).

I find it strange Intel are holding up the certification process, it seems odd to devote all this time to developing a new technology then impede it by not quickly allowing devices on the market. If there are few products available then it's no surprise companies aren't rushing to adopt the technology on their machines. I also agree the fire wire comparison seems apt, USB was good enough for most people but fire wire was superb if it suited your use, I much preferred the high performance for storage before esata and it was vastly better than USB for working dv camcorders.

The good:Yes, it is faster than USB, but not much. (Actually was as the newest USB3 standard is as fast as TB copper)Yes, it has some other qualities that are better on TB than on USB, but they are rather niche.

The bad:Can you hookup a mouse or keyboard on it? No, and even if was possible who would do such a beast when there's a 20-40$ extra cost just from communication chip.Is there a huge legacy peripheral ecosystem out there? Obviously not.When OEMs design a new economy model which one will see the axe first USB or TB? TB obviously as it is practicly impossible to make a PC without USB.

The only hope it has is if it could replace some other port like HDMI, but that too has too big thriving ecosystem to be possible.

TB is obviously the second coming of FireWire. Technical aspects aren't better enough to gain wide consumer usage and so the pricepoint on TB peripherals will be always higher even if the cabling problem can be solved. And it can't replace USB as a sole port.

I don't get it, What is Thunderbolt good for, exactly, that USB 3.0 or eSATA can't do just as well? Wikipedia tells me that Thunderbolt is 10Gbps to USB 3.0's 5Gbps, but what sort of peripheral in common use has any use for that much bandwidth?

You clearly never do any kind of large file transfers or work with video and audio. Thunderbolt has been a godsend for the professional (and prosumer) video and audio markets but they still need more. Your argumment is as ignorant as the famous "You'll never need more than 64KB of RAM" line from all those years ago.

Just because YOU seen no need for it, doesn't mean it isn't needed. Also, USB 3.0 VERY VERY VERY rarely ever manages to get anywhere close to it's 5Gbit theoretical limit. In my experience using various different controllers and devices it's slightly faster than FireWire 800 in actual practical use. Also don't forget that Thunderbolt is 10Gbit in 4 directions. It has two channels and each one is bi-directional, so you effectively have 40Gbit of bandwidth. USB 3.0 has 5Gbit. Tops. SATA 3.0 is 6Gbit, but that's useless for anything other than storage which makes sense because that's what it's made for. Thunderbolt is a do all approach.

You could make the same argument for SSD drives saying they were niche and who needs them when hard drives work just fine.

Yet here they are cheaper every day and taking over traditional drives. TB makes one controller for all connections. Removes clutter on the MB, reduces size and power constraints. will be ramped up to 20GB both ways sometime this year.....

They are actually pretty neat boxes and the idea of something like this plugged into a laptop is pretty compelling to me. But at $250 or $400, it just isn't a realistic option for me. Like TB in general, a lot of promise, but it seems a bit ahead of its time.

The good:Yes, it is faster than USB, but not much. (Actually was as the newest USB3 standard is as fast as TB copper)Yes, it has some other qualities that are better on TB than on USB, but they are rather niche.

The bad:Can you hookup a mouse or keyboard on it? No, and even if was possible who would do such a beast when there's a 20-40$ extra cost just from communication chip.Is there a huge legacy peripheral ecosystem out there? Obviously not.When OEMs design a new economy model which one will see the axe first USB or TB? TB obviously as it is practicly impossible to make a PC without USB.

The only hope it has is if it could replace some other port like HDMI, but that too has too big thriving ecosystem to be possible.

TB is obviously the second coming of FireWire. Technical aspects aren't better enough to gain wide consumer usage and so the pricepoint on TB peripherals will be always higher even if the cabling problem can be solved. And it can't replace USB as a sole port.

It is just like with FireWire.

USB 3 is almost as fast as Thunderbolt in theory. In reality, it is only as fast as one lane of Thunderbolt. USB also tends to load down the processor while Thunderbolt does not. If you were to fully saturate a Thunderbolt connection, it would, I believe, be around five times faster.

Thunderbolt support is still terrible in Mac OS. For example, when you do anything intensive: IO to a Pegasus RAID array, send data over the wired Ethernet, the USB audio goes to crap. Buzz, click, pfft, nothing. It seems like a buffering problem, as though USB cannot complete for buffer space and data slowly gets dropped down to almost nothing.

Want to listen to iTunes through your Thunderbolt display while doing any serious work? Forget about it. Apple claims to have fixed it, but they haven't. They're deaf to the complaints. I guess they don't use Skype, listen to iTunes, or do any other things related to audio while burning up the wires with IO.

I don't get it, What is Thunderbolt good for, exactly, that USB 3.0 or eSATA can't do just as well? Wikipedia tells me that Thunderbolt is 10Gbps to USB 3.0's 5Gbps, but what sort of peripheral in common use has any use for that much bandwidth?

You clearly never do any kind of large file transfers or work with video and audio. Thunderbolt has been a godsend for the professional (and prosumer) video and audio markets but they still need more. Your argumment is as ignorant as the famous "You'll never need more than 64KB of RAM" line from all those years ago.

Just because YOU seen no need for it, doesn't mean it isn't needed. Also, USB 3.0 VERY VERY VERY rarely ever manages to get anywhere close to it's 5Gbit theoretical limit. In my experience using various different controllers and devices it's slightly faster than FireWire 800 in actual practical use. Also don't forget that Thunderbolt is 10Gbit in 4 directions. It has two channels and each one is bi-directional, so you effectively have 40Gbit of bandwidth. USB 3.0 has 5Gbit. Tops. SATA 3.0 is 6Gbit, but that's useless for anything other than storage which makes sense because that's what it's made for. Thunderbolt is a do all approach.

AgreedI was on the edge with Thunderbolt till one of my clients purchased a Promise Pegasus....

As with most new expensive high performance connections it has its uses in the professional content creation industries. If you go to NAB and other such conferences you'll see the place is full of TB devices.

How many people fit into that niche? How many "average computer users" even know what NAB stands for? You've made the case for TB becoming "That port no one uses" just like FW was and still is. Sandy Bridge and Ivy Bridge motherboards have FW ports on them because why? one person out of 100 "might" use it? If we're talking a laptop, then why waste precious space for the 1%?

Thunderbolt support is still terrible in Mac OS. For example, when you do anything intensive: IO to a Pegasus RAID array, send data over the wired Ethernet, the USB audio goes to crap. Buzz, click, pfft, nothing. It seems like a buffering problem, as though USB cannot complete for buffer space and data slowly gets dropped down to almost nothing.

Want to listen to iTunes through your Thunderbolt display while doing any serious work? Forget about it. Apple claims to have fixed it, but they haven't. They're deaf to the complaints. I guess they don't use Skype, listen to iTunes, or do any other things related to audio while burning up the wires with IO.

The good:Yes, it is faster than USB, but not much. (Actually was as the newest USB3 standard is as fast as TB copper)Yes, it has some other qualities that are better on TB than on USB, but they are rather niche.

5Gb (which is what USB can theoretically get, but practically never do) vs. 40Gb (which is reportedly what TB can actually do). I think that qualifies as "much."

I also believe your second point isn't really accurate. TB is fundamentally different than USB. It is kind of like a generic pipe, allowing different standards to flow through the pipe. I guess I just don't see that as niche.

There are definitely flaws and problems with TB, but let's not downplay its very real advantages.

Edit: just read that the latest USB spec can theoretically do up to 10Gb. Still, that's 1/4 the ability of TB running on 4 lanes. And I'd be quite interested if it can achieve anything close to 10Gb in real world applications. More likely, it will get much less than that like existing USB 3 implementations.